A gate valve is a valve whose gate closing part moves in the vertical direction along the center line of the passage. It is generally composed of a valve body, a valve seat, a valve stem, a gate, a valve bonnet, and a sealing ring. It can be transformed into a variety of electric gate valves and pneumatic gate valves by equipping the transmission device and the gate valve. It can only be used for full opening and full closing in the pipeline, and cannot be used for adjustment and throttling.
Working Principle
The gate of the gate valve moves linearly with the valve stem. Usually there is a trapezoidal thread on the lifting stem. Through the nut at the top of the valve and the guide groove on the valve body, the rotary motion is converted into linear motion, that is, the operating torque is converted into operating thrust.
Closed
The sealing surface can be sealed only by the medium pressure, that is, the sealing surface of the gate is pressed against the valve seat on the other side by the medium pressure to ensure the sealing of the sealing surface. This is self-sealing. Most gate valves use forced sealing, that is, when the valve is closed, the gate is forced to press against the valve seat by external force to ensure the sealing of the sealing surface.
Open
When the gate lift height is equal to 1:1 times the valve diameter, the fluid passage is completely unblocked, but this position cannot be monitored during operation. In actual use, the top of the valve stem is used as a mark, that is, the position where it cannot be opened, as its fully open position. In order to consider the locking phenomenon caused by temperature changes, it is usually opened to the top position and then reversed 1/2-1 turn as the fully open valve position. Therefore, the fully open position of the valve is determined by the position of the gate (i.e. the stroke).
